Long-time Measurement of Resistance Spot Welding Current Based on Rogowski Coil

In order to realize long-time accurate measurement of resistance spot welding current and improve its engineering applicability, the circuit model of current measurement based on Rogowski coil was analyzed, and drift compensation methods were proposed for different offset characteristics of operational amplifiers. The effect of offset voltage and offset current on the integration drift of current measurement circuit was deduced based on superposition principle, and different drift compensation methods were designed for different offset characteristics of operational amplifiers. Experimental platform was established to verify the theoretical analysis of measurement circuit and drift compensation methods. The results show that the theoretical analysis of the relationship between measured current and output integral voltage is accurate with about-5% of relative error. The compensation methods can be applied to two different offset characteristics of operational amplifiers to realize long-time measurement of resistance spot welding current.